Fin-stabilized guidable missile

ABSTRACT

The present invention relates to a fin-stabilized missile ( 1 ) of the type which is intended to be fired at high acceleration towards a defined target along its trajectory and which can be guided in the trajectory and which, for stabilizing it in the trajectory, is provided with stabilizing fins ( 3, 32 ) arranged at its rear end, and control elements ( 6, 7 ) which are arranged at its front end and are intended to guide the latter, and whose rear part, in which the fins are secured, consists of a body part ( 4, 31 ) which can rotate freely relative to the main part ( 1, 29 ) of the missile about a bearing ( 14, 36 ) arranged concentric to the longitudinal axis (L) of the missile ( 1 ). According to the invention, said bearing ( 14, 36 ) is arranged near the dividing plane between the missile ( 1 ) and the body part ( 4, 31 ) and has a short length in the longitudinal direction of the missile, this having been made possible by the fact that it has been given a large diameter compared with its length and it has been designed with special load-bearing contact surfaces ( 20, 21, 27, 28 ) which limit the stresses during ramming and firing and during the flight of the missile ( 1 ) through the air. The freely rotatable body part ( 4, 31 ) for the fins ( 32 ) can then in turn be axially displaced from a launch position located inside the missile to a flight position where the fins ( 32 ) are pushed out behind the rear plane of the missile, where they can rotate freely.

The present invention relates to a novel type of fin-stabilized missileswhich can be guided in their respective trajectories towards apredetermined target. Guidable missiles here signify guidable artilleryshells, rockets or projectiles. These are assumed here to be of thegeneral type which are preferably fired without rotation, or at a lowinherent rotation about their longitudinal axis, and which, forstabilizing them in their trajectory towards the target, are assumed tobe provided with stabilizing fins which are arranged at the rear end andare initially retracted until the missile has completely exited thelaunch arrangement from which it has been fired, and can then bedeployed once it has left the launch arrangement completely. To guidethe missiles in pitch and yaw in their trajectories towards theirintended targets, they are also assumed to be provided with controlmembers arranged for this purpose preferably at their front end.

In many cases it is desirable, as it is in the present invention, to beable to guide missiles (for example shells, rockets or projectiles)towards a defined target while the missiles are in their trajectory.This can be done, for example, by guiding them in pitch and yaw by meansof control members arranged at the front end of the missile, and thesemembers can consist for example of canard fins, jet nozzles, etc.

Airborne missiles can be rotation-stabilized in their trajectory orstabilized in another way, for example by means of fins.Rotation-stabilized missiles have steady trajectories and they can bemade mechanically simple since the launch arrangement as a rule isresponsible for ensuring that the missile acquires the necessary initialrotation. However, the high rotational velocity has at least hithertomade it impossible to provide this type of missile with awell-functioning guidance system. When work is undertaken today todevelop effective guidable missiles, one has therefore concentratedefforts on missiles which do not rotate at all, or rotate only slowly,about their own longitudinal axis and which are aerodynamicallystabilized by means of fins arranged in their rear part.

In addition to stabilizing the missile flight, the stabilizing fins, ina fin-stabilized nonrotating missile, or in a missile rotating onlyslowly, can additionally give rise to an active lifting force which actson the missile and can be used to increase its range of fire.

A current trend in the development of artillery technology is towardsnew long-range artillery missiles guided in their final phase, andinterest has increased in different types of fin-stabilized shellsintended for firing in conventional guns and howitzers. To make itpossible to launch fin-stabilized shells with a low inherent rotationdirectly from grooved barrels, the shells need to be provided with adrive band as their only direct contact with the grooving of the barrel.The same gun or howitzer can thus be used, without special intermediatemeasures, to successively fire essentially nonrotating shells providedwith drive bands and with stabilizing fins, which can be deployed intrajectory, and entirely conventional rotation-stabilized shells.

In controlling the trajectory of fin-stabilized missiles such as shells,rockets and projectiles, it is necessary to know and be able to controlthe roll position of the missile. This in order to be able to controlthe missile in pitch and yaw. This control is achieved preferably withspecial control elements, for example in the form of movable nose fins,called canard fins, or jet nozzles. However, the roll control momentwhich such control elements in the front part of the missile give riseto can in many cases be counteracted or completely eliminated by theguide fins in the rear part of the missile, unless special measures aretaken. This is due to the fact that the vortices caused by the controlmoment from the rudder or other control activity impact the fins andthis in turn gives rise to a counteracting moment.

A way of solving this problem which has already been tested to an atleast limited extent is to let the part of the missile in which the finsare secured constitute a unit which can rotate freely in relation to therest of the missile about an axis concentric with the longitudinal axisof the missile. In this way, the effect of the control moment on thefins cannot be transferred to the front part of the missile, as a resultof which the missile is made easier to control.

From a purely practical point of view, it might be considered very easyto design a freely rotating bearing between the main part of the missileand a fin unit connected to the latter, but in reality this is not sucha straightforward matter—indeed it is extremely complicated—since allthe parts of the bearing have to be dimensioned in a way which takesinto account the stresses in the form of high acceleration anddeceleration which these parts have to tolerate both during ramming andduring launch, and the maximum forces which occur in these cases arealso effected in different directions.

The basic principle of the freely rotating fin unit has therefore to beregarded as already known at least in terms of its main features. Thepresent invention therefore relates more specifically to a missileprovided with a specially designed freely rotating fin unit. Theinvention is also in the first instance intended to be applied to afin-stabilized artillery shell, but it can also apply to any otherfin-stabilized and slowly rotating missile of the abovementioned generaltype. The particular characteristic feature of the fin-stabilizedmissile according to the invention is thus the design of the bearing forthe freely rotating fin unit. This bearing has now been designed totolerate the acceleration and deceleration forces during ramming of theshell and then the acceleration forces during firing of the shell.

The fin stabilizing unit forming part of the shell according to theinvention thus comprises a specific body part in which the fins aresecured and relative to which the fins can be retracted, and this bodypart can in turn rotate freely relative to the rest of the shell about abearing which is concentric to the longitudinal axis of the shell. Thisbearing in turn comprises a ball bearing or roller bearing in a singlebearing position with the greatest possible bearing diameter but with avery short length in the direction of flight of the missile, compared tosaid diameter, and this bearing position is additionally preferablyarranged as close as possible to the dividing plane, running transverseto the longitudinal direction of the missile, between the rest of themissile and the fin stabilizing unit which rotates freely relative tothe latter. The bearing which characterizes the invention moreovercomprises specially designed pairs of interacting contact surfaces inboth the main part of the shell and in the body part, arrangedperipherally with respect to the freely rotating fin unit and activatedin the axial direction upon maximum acceleration and decelerationstresses. In the preferred embodiment of the invention, these contactsurfaces are designed in such a way that the acceleration anddeceleration contact surfaces belonging to either the freely rotatingbody part or the main part of the missile are oriented in oppositedirections, which means that the contact surfaces in the body part aredirected towards each other while those in the main part of the missileare directed away from each other. In a development of the invention,there is also a specifically designed spring system whose task it is totake up within certain limits those forces which act in the longitudinaldirection of the shell between the rest of the missile and the body partof the fin unit and which act on these parts to move them away from eachother. This spring system, which acts between one of the parts and oneof the drive rings of the ball bearing, has the task of allowing theparts to rotate freely relative to each other even when they arestressed away from each other by a limited force, as will be the casewhen the missile is flying through the air with the fins deployed. Atthe same time the spring has a safety function in that it is intended toensure that the abovementioned contact surfaces engage with each otherbefore there is any risk of exceeding the maximum bearing load which theball bearing tolerates. As soon as said maximum bearing load approaches,the counter effect of the spring will have been exceeded and the partswill have been fixed relative to each other by means of the contactsurfaces having engaged with each other and the free mutual rotationhaving ceased. As soon as the excessive loading has ceased, the springwill then ensure that the parts return to their original positions andthe free mutual rotation again becomes possible.

The invention also includes a specific development in which the pointsof attachment of the fins consist of an axially displaceable body partwhich from a first retracted position inside the rear end of the missilebody in front of its usual rear plane can be pushed out to a seconddeployed position where the fins and their points of attachment aresituated behind said rear plane and where the fins are free to unfoldand where this body part at least in its pushed-out position can rotatefreely relative to the rest of the missile. Said body part can bedesigned as a cylinder which in the original position is thus insertedin a cylindrical cavity in the rear part of the missile. The detaileddesign of the body part can then vary depending on which fin type ischosen. With fins of the wrap-around type or folding-fin type, which arearranged along the outer periphery of the body part and are initiallyfolded in towards the latter, the body part can provide space for abase-bleed unit, while in other types of fins, for example those whichin the retracted position are folded into axial tracks in the body partabout axles transverse to the longitudinal axis, the base-bleed unit hasto be divided up into a number of smaller parts, which in turn will meanthat there is less space available for the base-bleed powder. With thebody part inserted into the rear part of the missile, there are lessstresses, when the missile is a shell, in particular on the bearingduring ramming in the barrel of the artillery piece since the drive bandof the shell can then be arranged on that part of the missile in whichthe body part is inserted in the original position.

To ensure that the system with an axially displaceable body part can atthe same time give a freely rotatable fin part, the body part mustcomprise a first body section and a second body section, where the firstbody section is axially displaceable, but not rotatably connected to therest of the missile, while the second body section is displaceabletogether with the first one and freely rotatable relative to it. Whenthe body part is displaced between its two positions, these two sectionsare thus displaced axially to a position where the second body sectionlies completely outside the original rear plane of the missile and inthis position the displacement of the first body section is locked forexample by means of an abutment flange or other type of deformation lockbetween the parts.

To activate the pushing-out of the fin-supporting body part from itsposition inside the rear end of the missile to its extended position,different methods can be used, for example in the form of expandingpyrotechnic gases. In a method which is particularly well suited toartillery shells, during the actual launch some of the powder gases fromthe propellant charge of the firing equipment are introduced via anarrow channel into a chamber between the push-out body part and therest of the missile, and after the missile has left the barrel and thepowder gas pressure behind the missile has ceased, the expansion ofthese powder gases is used to drive the body part out to its outerposition. The same method can also be used to remove a protective casingwhich during launch protects an axially immovable fin unit and which hasto be removed before the fins can be deployed. This method, which hasthe advantages that it provides an extremely rapid reaction associatedcompletely with the passage of the missile from the barrel muzzle, andthat it is entirely without any need for extra components, is alsodescribed in more detail in connection with the examples below.

The invention has been defined in its entirety in the attached patentclaims and it will now be described in some detail with reference to theattached figures, of which:

FIG. 1 shows a shell according to the invention on its way towards itstarget,

FIG. 2 shows in longitudinal section the rear part of the same shell asin FIG. 1, before being launched,

FIG. 3 shows the cross section along III—III in FIG. 2,

FIG. 4 shows the same details as in FIG. 2, but after launch, and withthe fins deployed,

FIG. 5 shows the circled part from FIG. 4 on a larger scale,

FIG. 6 shows a partial cross section through a missile with a fin unitwhich is displaceable in the longitudinal direction,

FIG. 7 shows the fin unit according to FIG. 6 in the retracted position,and

FIG. 8 shows the cross section VII—VII from FIG. 7.

The missile shown in FIG. 1, in this case the shell 1, is provided witha band track 2 for a drive band (this is generally lost when the shellleaves the barrel), a number of deployable fins 3 which are shown fullydeployed in the figure and which are fixed on a body part 4 whichrotates freely relative to the rest of the shell about an axisconcentric with the longitudinal axis of the shell. The dividing planebetween the shell 1 and the body part has been labelled 5. In addition,the shell 1 has two pairs of controllable canard fins 6 a, 6 b and 7 a,7 b arranged on a respective quadrant axis and with which the course andtrajectory of the shell can be corrected in accordance with controlcommands received either from an internal target seeker or from thelaunch site, via satellite, radar or other means. The way in which theshell receives control commands has nothing to do with the invention.This question will not therefore be mentioned again below.

FIGS. 2, 3 and 4 show in greater detail how the body part 4 isconstructed. Also included here are reference labels 2 for the band and5 for the dividing plane between the body part and the rest of theshell. As will be seen from the figures, the drive band of the shell inthis variant is placed on the body part 4 of the fin unit. This isbecause it is advantageous to have the drive band placed far back on ashell. The abovementioned dividing plane 5 will be returned to inconnection with FIG. 5. The fins 3 are shown in FIGS. 2 and 3 in theretracted position (see also FIGS. 4 and 5) in which they are covered bya removable casing 8. In the case shown in FIGS. 2 and 3, the casingcovers the fins and also a base-bleed unit 10 which is arranged in thecentre of the body part and whose charge of slow-burning powder here hasthe label 11 and its gas outlet has the label 12. As will be seen fromFIG. 3, the fins 3 in the retracted position are incurved towards theinside of the casing 8. In the casing 8 there is also a relativelynarrow gas inlet 13 which upon launch of the shells gives the barrelpressure, i.e. the powder gases from the propellant powder charge, freeaccess to that part of the inside 40 of the base-bleed unit which is nottaken up by its powder charge 11. At the same time the inlet and outlet13 in the casing 8 is so designed that when the shell leaves the barreland the pressure surrounding the shell quickly drops to atmosphericpressure, the gas expansion reaches inside the casing by means of thefact that the inlet and outlet 13 is so designed that the gases do notget out quickly enough, resulting in the casing being removed and thefins being released and deployed. This position is shown in FIG. 4. Aswill further be seen from the figures, the body part 4 is joined to therest of the shell via a ball bearing 14 whose outer ring 15 is securelyconnected to an annular component 9 which is fixed relative to the restof the shell. Since the drive band 2 of the shell in the variant shownin FIGS. 2-5 is mounted on the body part 4 of the fin unit, this bodypart 4 is drawn off from the main part of the shell 1 when rammed intothe launch equipment with great force (it must be anticipated that infuture all ramming will be done by mechanical rammers), while the bodypart 4, during launch, is instead pressed towards the main part of theshell 1 with a preferably even greater force. Both these forces wouldcertainly damage the bearing 14 if not taken up, and this is thereforeone of the aims of this invention.

To relieve the loading on the ball bearing 14 whose outer ring 15 isthus securely connected to the main part of the shell 1, the inner ring16 of the bearing is mounted on a bearing support 17 in such a way thatthe ring can easily slide axially. The bearing support 17 is in turnsecurely connected to the body part 4 of the fin unit, for example bymeans of a threaded connection 18. The bearing support 17 is furtherdesigned with a force-transmitting unit 19 which in the example shownhas a contact surface 20 frustoconical about its periphery and directedaway from the main part of the shell, which contact surface 20 facesacross a predetermined clearance to a correspondingly designed contactsurface 21 securely connected to the main part of the shell. These twocontact surfaces—the one labelled 20 in the fin unit being directedrearwards in the direction of flight of the shell, and the one labelled21 in the main part of the shell being directed forwards in thedirection of flight of the shell—now define, as they are broughttogether, the maximum distance by which the main part of the shell andthe fin unit can be displaced in the direction away from each other.

However, the arrangement according to the invention also includes twoopposing contact surfaces intended to limit the loading on the bearing14 when the main part of the shell 1 and the body part 4 of the fin unitare pressed towards each other. These two contact surfaces 27 and 28 liein the dividing plane 5.

When the shell is rammed into the equipment from which it is to befired, the fin unit is drawn rearwards relative to the rest of themissile, when the missile brakes upon ramming, since the body part ofthe fin unit comprises the drive band 2 which, during ramming, ispressed securely in the ramming position, while the main part of themissile has the greatest mass and a high velocity. In this position, thedistance between the contact surfaces 20 and 21 will disappear and thecontact surfaces will transmit all the loading between themselves. Thisis made possible by the fact that the bearing support and the inner ring16 of the bearing 14 are displaced relative to each other.

To permit a limited displacement of the main part of the shell 1 and thefin part (the body part 4) away from each other, but with a continuouslyfunctioning ball bearing 14, the arrangement according to the inventionhas been supplemented, in a particularly preferred embodiment, with aspring unit 22 in the form of a specially designed annular spring ortubular spring with an L-shaped cross section and with a first tubularpart 23 via which it is connected by an internal thread 24 to thecylindrical outside 25 of the bearing support 17, and a second resilientplane annular limb 26 whose inner edge lies against the inner ring 16 ofthe ball bearing 14 and there counteracts a displacement of the mainpart of the shell 1 and the fin unit (the body part 4) away from eachother. As long as this spring unit 22 is tensioned but has not yetreached the bottom position of the displacement possibility, the finunit will thus be able to rotate freely via the ball bearing 14. Thepossibility of rotation with a tensioned spring unit will apply inparticular when the shell is flying through the air and the air flowingpast acts on the fins 3. In this position, the spring unit will betensioned but only so much that the bearing 14 still functions. If theload which the spring unit tolerates is exceeded, then the contactsurfaces 20 and 21 come together and the possibility of rotation ceases,but at the same time the ball bearing is relieved of increased loading.

Instead, the fin unit is pressed towards the main part of the shellduring launch, and the contact surfaces 27 and 28 engage with eachother. The ball bearing 14 at the same time slides on the bearingsupport until its force-transmitting unit 19 comes to support the innerring 16 of the bearing. The distance between the contact surfaces 27 and28 and between the inner ring 16 and the force-transmitting unit 19 ofthe bearing support is almost identical. The tolerances must be suchthat the difference is less than the axial play in the bearing 14.

The shell illustrated in FIGS. 6, 7 and 8 can still have its main partlabelled 1 and it is provided in its rear part, here labelled 29, with adrive band 2. A cavity 30 is arranged in the rear part 29 of the shell.A specially configured fin body 33 is arranged inside this cavity untilthe shell has left the artillery piece in which it is fired. The finbody with its retracted fins is shown in the retracted position in FIGS.7 and 8. There are eight fins here and they are all labelled 32. Eachone of them lies in its own track 37 in the body part 31 and they can bedeployed outwards and rearwards about their axes 33, in the mannerindicated by the arrows A in FIG. 7. The special feature of the variantof the invention shown in these figures is that the fin body 31 hereconsists of a front section 34 and a rear section 35 which are rotatablerelative to each other with a ball bearing 36 between them correspondingto the type in the previously described variant of the invention.However, because of the position of the drive band 2, the system forrelieving the forces on the bearing 36 can be made slightly simpler thanin the previous variant.

The special feature of this variant of the invention is that when theshell has left the artillery piece from which it is fired the whole ofthe fin body 31 is displaced from its fully retracted position in thespace 30 to a position where only its front section 34 is left in itsoutlet, where it is blocked by means of a deformation joint of one typeor another, while the whole of the rear part 35 of the fin body islocated behind the original rear plane B of the shell and where the fins32 are deployed in the manner indicated in FIG. 7 and the rear part ofthe body in which they are secured is allowed to rotate freely relativeto the main part of the shell about the bearing 36 concentric with thelongitudinal axis of the shell. For pushing the body part 31 out to itsrear position, the propellant powder gases are used which as previouslydescribed, are allowed during launch, to flow via the channel 39 intothe inner chamber which is labelled 38.

An advantage of this variant is that the fins reach further away fromthe centre of gravity of the missile and in this way the fins can bemade smaller while retaining the stability of the missile.

What is claimed is:
 1. Fin-stabilized missile (1) which is intended tobe fired at high acceleration towards a target alone its trajectory andwhich can be guided in the trajectory, comprising: a main part and arear part; stabilizing fins (3, 32) arranged at a rear end of themissile for stabilizing the missile; and control elements (6, 7) whichare arranged at a front end of the missile and are arranged to guide themissile, wherein the rear part of the missile comprises a body part (4,31) which can rotate freely relative to the main part (1, 29) of themissile about a bearing (14, 36) arranged concentric to the longitudinalaxis (L) of the missile (1), the stabilizing fins are secured to therear part of the missile, the bearing (14, 36) is arranged near adividing plane between the body part (4, 31) and a remainder of themissile (1) and has a large diameter compared with its length in thelongitudinal direction of the missile, the bearing is designed with aslight axial clearance, both forwards and rearwards of the bearing, inthe main part of the missile and in said body part there are peripheralannular contact surfaces (20, 21 and 27, 28) which in pairs are broughtto bear against each other immediately before said axial clearancereaches its respective end positions in the bearing in order to transferforces acting between the main part (1, 29) of the missile and said bodypart (4, 31) or parts thereof, contact surfaces (20, 21) which limit theremoval of the main part (1) of the missile and the body part (4) fromeach other are frustoconical in shape, and contact surfaces (27, 28)which limit the pressing-together of the two parts are flat and annular.2. Fin-stabilized missile according to claim 1, wherein a first bodysection (35) is rotatably mounted via the bearing (36) in a secondspecial front body section (34) which does not rotate relative to therest of the missile, and after the missile has left a launch arrangementthe body sections (35, 36) can be displaced together from a firststarting position, where both the body sections are situated inside aspace (30) in the rear part of the missile, to a second trajectoryposition where the first body section (35) is situated completely behindthe original rear plane of the missile, while the second front bodysection (34) is locked relative to the rest of the missile near theoriginal rear plane.
 3. Fin-stabilized missile (1) according to claim 1,comprising: a component (8, 34-35) which can be displaced relative tothe rest of the missile wherein after die missile (1) has left thebarrel of a launch arrangement, the component is displaced axially froma first position to a second position, and; a chamber (40, 38) which isarranged between said component and an inner base plane and to whichthere leads an inlet channel (13, 39) with a limited cross-sectionalarea, through which the chamber (40, 38) during launch inside a barrelis supplied with propellant powder gases under high pressure which, whenthe pressure outside the chamber drops as soon as the missile has leftthe barrel, will effect the desired displacement of the component. 4.Fin-stabilized missile according to claim 1, wherein the pairs ofmutually interacting contact surfaces which limit the movements of theparts (1, 4 and 34, 35) relative to each other are arranged at differentaxial distances from the bearing and also partially overlap each otherin the radial direction.
 5. Fin-stabilized missile according to claim 1,wherein the bearing (14, 36) comprises a ball bearing (14, 36) with anouter ring (15) clamped securely in the main part (1, 29) of the missileand an inner ring (16) connected to the body part via an attachment,which gives a limited mobility in the axial direction forwards andrearwards in the flight direction of the missile (1), and movement ofthe main part (1, 29) of the missile and the body part away from eachother is counteracted by a spring arrangement (22) clamped between thebody part (4) and the inner ring (16) of the ball bearing (14). 6.Fin-stabilized missile according to claim 1, wherein the axial clearancein the pressing direction between the peripheral annular contactsurfaces (27, 28) does not exceed the axial play of the ball bearing. 7.Fin-stabilized missile (1) which is intended to be fired at highacceleration towards a target alone its trajectory and which can beguided in the trajectory, comprising: a main part and a rear part;stabilizing fins (3, 32) arranged at a rear end of the missile forstabilizing the missile; and control elements (6, 7) which are arrangedat a front end of the missile and are arranged to guide the missile,wherein the rear part of the missile comprises a body part (4, 31) whichcan rotate freely relative to the main part (1, 29) of the missile abouta bearing (14, 36) arranged concentric to the longitudinal axis (L) ofthe missile (1), the stabilizing fins are secured to the rear part ofthe missile, the bearing (14, 36) is arranged near a dividing planebetween the body part (4, 31) and a remainder of the missile (1) and hasa large diameter compared with its length in the longitudinal directionof the missile, the bearing is designed with a slight axial clearance,both forwards and rearwards of the bearing, in the main part of themissile and in said body part there are peripheral annular contactsurfaces (20, 21 and 27, 28) which in pairs are brought to bear againsteach other immediately before said axial clearance reaches itsrespective end positions in the bearing in order to transfer forcesacting between the main part (1, 29) of the missile and said body part(4, 31) or parts thereof, and the pairs of mutually interacting contactsurfaces which limit the movements of the parts (1, 4 and 34, 35)relative to each other are arranged at different axial distances fromthe bearing and else partially overlap each other in the radialdirection.
 8. Fin-stabilized missile according to claim 7, wherein thebearing (14, 36) comprises a ball bearing (14, 36) with an outer ring(15) is clamped securely in the main part (1, 29) of the missile and aninner ring (16) connected to the body part via an attachment, whichgives a limited mobility in the axial direction forwards and rearwardsin the flight direction of the missile (1), and movement of the mainpart (1, 29) of the missile and the body part away from each other iscounteracted by a spring arrangement (22) clamped between the body part(4) and the inner ring (16) of the ball bearing (14).
 9. Fin-stabilizedmissile according to claim 7, wherein the axial clearance in thepressing direction between the peripheral annular contact surfaces (27,28) does not exceed the axial play of the ball bearing. 10.Fin-stabilized missile according to claim 7, wherein a first bodysection (35) is rotatably mounted via the bearing (36) in a secondspecial front body section (34) which does not rotate relative to therest of the missile, and slier the missile has left a launch arrangementthe body sections (35, 36) can be displaced together from a firststarting position, where both the body sections are situated inside aspace (30) in the rear part of the missile, to a second trajectoryposition where the first body section (35) is situated completely behindthe original rear plane of the missile, while the second front bodysection (34) is locked relative to the rest of the missile near theoriginal rear plane.
 11. Fin-stabilized missile (1) according to claim7, comprising: a component (8, 34-35) which can be displaced relative tothe rest of the missile, wherein after the missile (1) has left thebarrel of a launch arrangement, the component is displaced axially froma first position to a second position and; a chamber (40, 38) which isarranged between said component and an inner base plane and to whichthere leads an inlet channel (13, 39) with a limited cross-sectionalarea, through which the chamber (40, 38) during launch inside a barrelis supplied with propellant powder gases under high pressure which, whenthe pressure outside the chamber drops as soon as the missile has leftthe barrel, will effect the desired displacement of the component. 12.Fin-stabilized missile (1) which is intended to be fired at highacceleration towards a target alone its trajectory and which can beguided in the trajectory, comprising: a main part and a rear part;stabilizing fins (3, 32) arranged at a rear end of the missile forstabilizing the missile; control elements (6, 7) which are arranged at afront end of the missile and are arranged to guide the missile; whereinthe rear part of the missile comprises a body part (4, 31) which canrotate freely relative to the main part (1, 29) of the missile about abearing (14, 36) arranged concentric to the longitudinal axis (L) of themissile (1), the stabilizing fins are secured to the rear part of themissile, the bearing (14, 36) is arranged near a dividing plane betweenthe body part (4, 31) and a remainder of the missile (1) and has a largediameter compared with its length in the longitudinal direction of themissile, the bearing is designed with a slight axial clearance, bothforwards and rearwards of the bearing, in the main part of the missileand in said body part there are peripheral annular contact surfaces (20,21 and 27, 28) which in pairs are brought to bear against each otherimmediately before said axial clearance reaches its respective endpositions in the bearing in order to transfer forces acting between themain part (1, 29) of the missile and said body part (4, 31) or partsthereof, the bearing (14, 36) comprises a ball hearing (14, 36) with anouter ring (15) clamped securely in the main part (1, 29) of the missileand whose in inner ring (16) connected to the body part via anattachment, which gives a limited mobility in the axial directionforwards and rearwards in the flight direction of the missile (1), andmovement of the main part (1, 29) of the missile and die body part awayfrom each other is counteracted by a spring arrangement (22) clampedbetween the body part (4) and the inner ring (16) of the ball bearing(14).
 13. Fin-stabilized missile (1) according to claim 12, wherein saidspring arrangement (22) is designed to accept a certain loading ofmissile and body part away from each other and associated displacementbetween them before the contact surfaces (20, 21) acting in thisdirection bear against each other, where said ball bearing (14) is atthe same time adapted to take up forces acting between the outer ring(15) and inner sing (16).
 14. Fin-stabilized missile according to claim13, wherein the inner ring (16) of the same ball bearing is arranged ona bearing support (17) securely connected to said body part and, whenthe main part of the missile (1) and the body part (4) are loaded in thedirection away from each other, it displaces counter to said springarrangement (22) within certain predetermined limits within which theball bearing (14) gives the desired free rotation for the body part (4)relative to the main part of the missile (1).
 15. Fin-stabilized missileaccording to claim 13, wherein said spring arrangement (22) consists ofan annular spring of L-shaped cross section with a first lamb (23) whichextends rearwards in the direction of flight of the missile and which issecured to the body part (4), and a second resilient limb (26) whichextends radially in towards the center of the bearing and lies againstthe edge of the inner ring (16) of the ball bearing which is directedforwards in the direction of flight of the missile.
 16. Fin-stabilizedmissile according to claim 12, wherein the inner ring (16) of the ballbearing is arranged on a bearing support (17) securely connected to saidbody part and, when the main part of the missile (1) and the body part(4) are loaded in the direction away from each other, it displacescounter to said spring arrangement (22) within certain predeterminedlimits within which the ball bearing (14) gives the desired freerotation for the body part (4) relative to the main part of the missile(1).
 17. Fin-stabilized missile according to claim 16, wherein saidspring arrangement (22) comprises an annular spring of L-shaped crosssection with a first limb (23) which extends rearwards in the directionof flight of the missile and which is secured to the body part (4), anda second resilient limb (26) which extends radially in towards thecenter of the bearing and lies against the edge of the inner ring (16)of the ball bearing which is directed forwards in the direction offlight of the missile.
 18. Fin-stabilized missile according to claim 12,wherein the axial clearance in the pressing direction between theperipheral annular contact surfaces (27, 28) does not exceed the axialplay of the ball bearing.
 19. Fin-stabilized missile according to claim12, wherein said spring arrangement (22) comprises an annular spring ofL-shaped cross section with a first limb (23) which extends rearwards inthe direction of flight of the missile and which is secured to the bodypart (4), and a second resilient limb (26) which extends radially intowards the center of the bearing and lies against the edge of the innerring (16) of the ball bearing which is directed forward in the directionof flight of the missile.
 20. Fin-stabilized missile according to claim12, wherein a first body section (35) is rotatably mounted via thebearing (36) in a second special front body section (34) which does notrotate relative to the rest of the missile, and after the missile hasleft a launch arrangement the body sections (35, 36) can be displacedtogether from a first starting position, where both the body sectionsare situated inside a space (30) in the rear part of the missile, to asecond trajectory position where the first body section (35) is situatedcompletely behind the original rear plane of the missile, while thesecond front body section (34) is locked relative to the rest of themissile near the original rear plane.